Granular forms of Bayleton (or any systemic fungicide) will take a couple days to begin working. In this case, the plant wasn't coated with fungicide bsuch as with a liquid, but rather you probably instructed the client to water the product into the root zone. Therefore the crown & roots must absorb the Bayleton & then the plant must translocate the fungicide. But this really doesn't happen at all. All the Sterol inhibitting fungicides can do is behave as a local penetrant. The crown was the only place where penetration might be benefitting the situation. So if infection is on the upper portion of a grass plant, then the short term results would be minimal at best.
That said, look at the lawn in the early AM yourself. Pythium exhibits a cottony mycelium too. Bayleton does nothing for Pythium.
Small spiders are found inhabitting turf too. Their webs are often mistaken for mycelium. The customer almost certainly can't tell the difference.